Not listing Linux 64 bit in operating system menu

[Rosh]

My machine is windows 7 64 bit . I wanted to create a virtual machine for cisco csr1000v router.

The VM settings for the CSR are :

OS: Other Linux (64-bit)
RAM: 2560-4096 MB (as of 3.10, a minimum of 2.5 GB is supported for basic operation)
Hard Disk: 8GB IDE

But while selecting OS it lists only Linux (32-bit) and not listing 64-bit as in specification.

Hence when I start vm it ends with error
" This kernel requires an x86-64 CPU ,but only detected an i686 CPU.Unable to boot- please use a kernel appropriate for your cpu"-

Please help me to correct this issue

[loukingjr]

See: I have a 64bit host, but can't install 64bit guests